C. Delvaux

A very luminous magnetar-powered supernova associated with an ultra-long gamma-ray burst

A new class of ultra-long-duration (more than 10,000 seconds) γ-ray bursts has recently been suggested. They may originate in the explosion of stars with much larger radii than those producing normal long-duration γ-ray bursts or in the tidal disruption of a star. No clear supernova has yet been associated with an ultra-long-duration γ-ray burst. Here we report that a supernova (SN 2011kl) was associated with the ultra-long-duration γ-ray burst GRB 111209A, at a redshift z of 0.677. This supernova is more than three times more luminous than type Ic supernovae associated with long-duration γ-ray bursts, and its spectrum is distinctly different. The slope of the continuum resembles those of super-luminous supernovae, but extends further down into the rest-frame ultraviolet implying a low metal content. The light curve evolves much more rapidly than those of super-luminous supernovae. This combination of high luminosity and low metal-line opacity cannot be reconciled with typical type Ic supernovae, but can be reproduced by a model where extra energy is injected by a strongly magnetized neutron star (a magnetar), which has also been proposed as the explanation for super-luminous supernovae.

Gamma-Ray Bursts trace uv metrics of star formation over 3 < z < 5

We present the first uniform treatment of long duration gamma-ray burst (GRB) host galaxy detections and upper limits over the redshift range , a key epoch for observational and theoretical efforts to understand the processes, environments, and consequences of early cosmic star formation (SF). We contribute deep imaging observations of 13 GRB positions yielding the discovery of 8 new host galaxies. We use this data set in tandem with previously published observations of 31 further GRB positions to estimate or constrain the host galaxy rest-frame ultraviolet (UV; ?) absolute magnitudes . We then use the combined set of 44 estimates and limits to construct the luminosity function (LF) for GRB host galaxies over and compare it to expectations from Lyman break galaxy (LBG) photometric surveys with the Hubble Space Telescope. Adopting standard prescriptions for the luminosity dependence of galaxy dust obscuration (and hence, total SF rate), we find that our LF is compatible with LBG observations over a factor of 600? in host luminosity, from = ?22.5 mag to >?15.6 mag, and with extrapolations of the assumed Schechter-type LF well beyond this range. We review proposed astrophysical and observational biases for our sample, and find that they are for the most part minimal. We therefore conclude, as the simplest interpretation of our results, that GRBs successfully trace UV metrics of cosmic SF over the range . Our findings suggest that GRBs provide an accurate picture of star formation processes from out to the highest redshifts.

Super-solar metallicity at the position of the ultra-long GRB 130925A

Over the last decade there has been immense progress in the follow-up of short and long gamma-ray bursts (GRBs), resulting in a significant rise in the detection rate of X-ray and optical afterglows, in the determination of GRB redshifts, and of the identification of the underlying host galaxies. Nevertheless, our theoretical understanding of the progenitors and central engines powering these vast explosions is lagging behind, and a newly identified class of ultra-long GRBs has fuelled speculation on the existence of a new channel of GRB formation. In this paper we present high signal-to-noise X-shooter observations of the host galaxy of GRB 130925A, which is the fourth unambiguously identified ultra-long GRB, with prompt -ray emission detected for 20 ks. The GRB line of sight was close to the host galaxy nucleus, and our spectroscopic observations cover this region along the bulge/disk of the galaxy, and a bright star-forming region within the outskirts of the galaxy. From our broad wavelength coverage, we obtain accurate metallicity and dust-extinction measurements at the galaxy nucleus and at an outer star-forming region, and measure a super-solar metallicity at both locations, placing this galaxy within the 10 20% most metal-rich GRB host galaxies. Such a high metal enrichment has significant implications on the progenitor models of both long and ultra-long GRBs, although the edge-on orientation of the host galaxy does not allow us to rule out a large metallicity variation along our line of sight. The spatially resolved spectroscopic observations presented in this paper offer important insight into variations in the metal and dust abundance within GRB host galaxies. However, they also illustrate the need for integral field unit observations on a larger sample of GRB host galaxies of a variety of metallicities to provide a more quantitative view on the relation between the GRB circumburst environment and the galaxy-whole properties.

The Optical/NIR afterglow of GRB 111209A: Complex yet not Unprecedented

Context. Afterglows of gamma-ray bursts (GRBs) are simple in the most basic model, but can show many complex features. The ultra-long duration GRB 111209A, one of the longest GRBs ever detected, also has the best-monitored afterglow in this rare class of GRBs. nAims. We want to address the question whether GRB 111209A was a special event beyond its extreme duration alone, and whether it is a classical GRB or another kind of high-energy transient. The afterglow may yield significant clues. nMethods. We present afterglow photometry obtained in seven bands with the GROND imager as well as in further seven bands with the Ultraviolet/Optical Telescope (UVOT) on-board the Neil Gehrels Swift Observatory. The light curve is analysed by multi-band modelling and joint fitting with power-laws and broken power-laws, and we use the contemporaneous GROND data to study the evolution of the spectral energy distribution. We compare the optical afterglow to a large ensemble we have analysed in earlier works, and especially to that of another ultra-long event, GRB 130925A. We furthermore undertake a photometric study of the host galaxy. nResults. We find a strong, chromatic rebrightening event at ≈0.8 days after the GRB, during which the spectral slope becomes redder. After this, the light curve decays achromatically, with evidence for a break at about 9 days after the trigger. The afterglow luminosity is found to not be exceptional. We find that a double-jet model is able to explain the chromatic rebrightening. The afterglow features have been detected in other events and are not unique. nConclusions. The duration aside, the GRB prompt emission and afterglow parameters of GRB 111209A are in agreement with the known distributions for these parameters. While the central engine of this event may differ from that of classical GRBs, there are multiple lines of evidence pointing to GRB 111209A resulting from the core-collapse of a massive star with a stripped envelope.

Multi-wavelength properties of IGR J05007−7047 (LXP 38.55) and identification as a Be X-ray binary pulsar in the LMC

We report on the results of a

Long optical plateau in the afterglow of the short GRB 150424A with extended emission - Evidence for energy injection by a magnetar?

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EXTraS discovery of two pulsators in the direction of the LMC: a Be/X-ray binary pulsar in the LMC and a candidate double-degenerate polar in the foreground

40 d multi-wavelength monitoring of the Be X-ray binary system IGR J05007-7047 (LXP 38.55). During that period the system was monitored in the X-rays using the Swift telescope and in the optical with multiple instruments. When the X-ray luminosity exceeded

Microphysics and dynamics of the gamma-ray burst 121024A

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Large-amplitude late-time radio variability in GRB 151027B

erg/s we triggered an XMM-Newton ToO observation. Timing analysis of the photon events collected during the XMM-Newton observation reveals coherent X-ray pulsations with a period of 38.551(3) s (1 {sigma}), making it the 17

Highly Luminous Supernovae associated with Gamma-Ray Bursts I.: GRB 111209A/SN 2011kl in the Context of Stripped-Envelope and Superluminous Supernovae

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